Abstract: With two-dimensional （2D） particle-in-cell simulations, the excitation of electrostatic waves by two-beam instability, and their nonlinear evolution into the electrostatic solitary waves are investigated. The simulation results indicate that the electrostatic waves excited in linear growth stage propagate mainly along the magnetic field. These waves coalesce with each other and form electrostatic solitary waves, and at the same time they can generate electrostatic whistlers. Moreover, we have also surveyed the influence of the strength of the magnetic field and the ion temperature on this process. Electrostatic solitary waves cannot form when the strength of the magnetic field is weak. Only if the strength of the magnetic field is sufficiently strong can the electrostatic waves form. Meanwhile, the ion temperature can affect the stability of electrostatic solitary waves. When the ion temperature is low, the stability of electrostatic solitary waves decrease and they will break up gradually.